In recent years, for example, the diameter of semiconductor wafers (hereinafter, referred to as “wafers”) are increasing. In addition, there is a desire to make the wafers thin in a specified process such as mounting or the like. However, a large-diameter thin wafer is likely to be bent or cracked if the wafer is transferred or polished as is. As such, for example, in order to reinforce the wafer, the wafer is bonded to, for example, a wafer or a glass substrate that acts as a support substrate. Thereafter, a predetermined process such as a polishing process is performed on the wafer in a state where the wafer is bonded to the support substrate as described above, and subsequently, the wafer and the support substrate are peeled off from each other.
Such a peeling process is performed, for example, using a peeling apparatus. For example, Patent Document 1 discloses a peeling device which can be used which directly bonds a wafer with devices formed thereon to a wafer with a thermal oxide film formed thereon, followed by performing a peeling process on the bonded wafer. The peeling device includes a first holder for holding the wafer, a second holder for holding the support substrate, and a nozzle for injecting liquid between the wafer and the support substrate. In the peeling device, the nozzle injects liquid between the wafer and the support substrate which are bonded together, i.e., a bonding surface between the wafer and the support substrate, at an injection pressure which is greater than a bonding strength applied in bonding the wafer and the support substrate, preferably, at an injection pressure that is two or more times stronger than the bonding strength, thus peeling the wafer and the support.
In addition to the method of directly bonding the wafer to a support substrate with the thermal oxide film formed thereon, there is a method of bonding the wafer and the support substrate, a method of bonding a support substrate and a wafer by applying an adhesive therebetween.
If the adhesive is used for the bonding, when the wafer and the support substrate are peeled off from each other, the adhesive applied between the wafer and the support substrate needs to be softened. For this reason, when the wafer and the support substrate are peeled off, heating is applied to the bonded wafer to soften the adhesive.
However, when the wafer is heated, oxidation is rapidly progressed on a surface (bonding surface) of the bonded wafer exposed by the peeling. Such a rapid oxidation may cause a serious damage to a product.
Prevention of such damage to the product from the rapid oxidation requires decreasing a concentration of oxygen around the wafer when the peeling is performed. However, in order to decrease oxygen concentration to prevent the rapid oxidation, it is necessary to cover the wafer and the peeling device with an airtight container. This causes an increase in size of the apparatus, which results in an increased installation space, an increased installation cost, and a reduction in throughput.
As a method of preventing the rapid oxidation of the wafer without using the airtight container, there is a method which directly injects an inert gas or the like to the wafer after the peeling, for example using a slit-shaped nozzle. However, when the inert gas is injected to the wafer by the slit-like nozzle, a flow rate of the inert gas injected from the nozzle causes circumambient air to be sucked into the peeling device. However, due to the air approaching the bonding surface of the wafer along with the inert gas, the inert gas cannot be injected to the bonding surface of the wafer.